What Mods Have You Done?
You'll have to list the mods to the engine, and any codes to get more accurate information. Whith that said, a guess would be that the EEC-IV is having a hard time trying to find the proper air/fuel mixture at a given RPM. If you've change out anything recently, this a normal function of the EEC, as it is trying to adjust itself to the readings its getting from the sensors. The sensor outputs are expected values, so if you have a device that is functioning outside of this range (i.e. a TB that is bigger), the TPS reading for the air flow going past it is not in sync. Note that air past the TB/TP can come from any place in the intake system if there is a leak). Normally, the IAC or the sample tube is letting too much or too little air in at idle due to a slow acting or poor sealing piston, or with the sample tube, the wrong size. My guess is that the TB's TP is amiss and is not seated fully closed and the TPS is not reading 0.8V with TP fully closed, and the IAC/sample tube is providing the wrong amount of intake air at idle. Also, the IC tubes leaking, if the leak is bad enough, the SC bypass valve will flucuate from its fully open positon from loss of vacuum towards the closing position, which will cause strange idle problems as well.